The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Encoding of data for a video generally involves an intra prediction encoding and an inter prediction encoding. The intra prediction encoding and the inter prediction encoding are effective methods capable of reducing the correlation existing between multiple pieces of data, which are widely used in various data compressions. Especially, in the inter prediction encoding, since a motion vector of a current block determined through estimation of the motion of the current block to be currently encoded has a close relation with motion vectors of the surrounding blocks, a predicted motion vector (PMV) for the motion vector of the current block is first calculated from the motion vectors of the surrounding blocks and only a differential motion vector (DMV) for the PMV is encoded instead of encoding the motion vector of the current block itself, so as to considerably reduce the quantity of bits to be encoded and thus improve the encoding efficiency.
That is, in the case of performing the inter prediction encoding, an encoder encodes and transmits only a DMV corresponding to a differential value between the current motion vector and a PMV determined through estimation of the motion of the current block from a reference frame, which has been reconstructed through previous encoding and decoding. A decoder reconstructs the current motion vector by adding the PMV and the DMV transmitted based on a prediction of the motion vector of the current block using the motion vectors of the surrounding blocks previously decoded.
Further, at the time of performing the inter prediction encoding, the resolution may be enhanced en bloc through interpolation of the reference frame, and a DMV corresponding to a differential value between the current motion vector and a PMV determined through estimation of the motion of the current block may then be encoded and transmitted. In this event, the enhancement of the resolution of a reference video (i.e. the video of the reference frame) enables a more exact inter prediction and thus reduces the quantity of bits generated by the encoding of the residual signal between the original video and a predicted video. However, the enhancement of the resolution of the reference video also causes an enhancement of the resolution of the motion vector, which increases the quantity of bits generated by the encoding of the DMV. In contrast, although a decrease of the resolution of the reference video increases the quantity of bits generated by the encoding of the residual signal, it decreases the resolution of the motion vector, resulting in the corresponding decrease of the quantity of bits generated by encoding of the DMV.
As described above, since the conventional inter prediction encoding uses motion vectors of the same resolution obtained by interpolating all video encoding units, such as blocks, slices, and pictures, of a video with the same resolution, it is difficult for the conventional inter prediction encoding to achieve an efficient encoding, which may degrade the compression efficiency.